Small air conditioners typically utilize economical fixed capacity compressors. Because the cooling and heating needs served by such systems vary it is common practice to provide a control which turns the fixed capacity compressor on and off intermittently to match variations in the process load. However, that causes corresponding fluctuations in process conditions such as temperature and humidity. To minimize such on-off cycling, heat discharged from the compressor is sometimes added to the process load so that the compressor does not turn off but continues to operate with an excess component which offsets and is wasted by the false heat load component. This is known as a hot gas by-pass system and because it is energy wasteful it is discouraged if not prohibited by some current building codes.
No prior art air conditioning and heat pump system has been capable of controlling process temperature and humidity with a fixed capacity compressor without cycling the compressor on and off with great frequency or without wasting energy by false loading. Both have marked disadvantages. Utilization of thermal storage for cyclic peak shaving can be a solution to this problem but heretofore it has not been applied to fixed capacity air conditioning systems for control of both cooling and heating parameters.
In U.S. Pat. No. 4,761,967 an air conditioning system is described wherein coolness is stored for short periods and utilized to avoid intermittent cycling of the refrigeration systems. However, it is confined to an automotive air conditioning system which does not store both heat and coolness simultaneously or employ fixed capacity refrigeration. Instead it stores only coolness when its variable capacity compressor is operating at excess capacity for later discharge when the compressor capacity is low or turned off. U.S. Pat. No. 4,187,904 concerns intermittent storage of heat for later potential use in heating a building. However, it is not concerned with air conditioning and does not involve the storage of coolness. U.S. Pat. No. 3,523,575 concerns a fixed capacity air conditioning system wherein heat energy is stored over long periods of time from a refrigerant cycle. However, that system does not involve storage of coolness nor the simultaneous heating and cooling of air.
None of these teachings of the prior art is capable of controlling dew point and dry bulb temperatures within an air conditioning system independent of process load variations while utilizing a fixed capacity refrigeration system and without the use of a hot gas by-pass or other false loading technique.